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The report comes from a nonpartisan group of researchers called PropOrNot. The group describes itself as "concerned American citizens" with expertise in computer science, national security and public policy. The researchers say they traced the origins of posts and mapped the connections among accounts that delivered similar messages.

The findings show just how effective the bogus reports and propaganda were, according to the report. On Facebook, PropOrNot estimates that stories planted or promoted by the disinformation campaign were viewed 213 million times.

While it's not clear whether fake news and propaganda helped sway the election in Trump's favor, millions of Americans get their news from what's shared on Facebook and other social media. In recent months, fake and misleading stories have proliferated, even as Facebook has insisted that they make up a tiny fraction of the overall stuff users share on the site.

Both Facebook and Google have said they are taking steps to stop the spread of misinformation on their sites, including by turning off access to advertising.

PropOrNot's report, provided to The Post in advance of its public release, identified more than 200 websites as "peddlers of Russian propaganda during the election season, with combined audiences of at least 15 million Americans."

PropOrNot did immediately not respond to a message asking for the report on Friday afternoon.